private void computeBandIndexes(Granule g) {
if (g.blockType == 2) {
if (g.switchPoint != 0) {
if (ctx.header.sampleRateIndex == 8) {
log.warn(String.format("Unimplemented switch point in 8kHz"));
}
// if switched mode, we handle the 36 first samples as
// long blocks. For 8000Hz, we handle the 72 first
// exponents as long blocks
if (ctx.header.sampleRateIndex <= 2) {
g.longEnd = 8;
} else {
g.longEnd = 6;
}
g.shortStart = 3;
} else {
g.longEnd = 0;
g.shortStart = 0;
}
} else {
g.shortStart = 13;
g.longEnd = 22;
}
}
// main layer3 decoding function
private int decodeLayer3(int frameStart) {
int mainDataBegin;
int nbGranules;
int[] exponents = new int[576];
Mp3Header s = ctx.header;
// read side info
if (s.lsf != 0) {
mainDataBegin = br.read(8);
br.skip(s.nbChannels);
nbGranules = 1;
} else {
mainDataBegin = br.read(9);
if (s.nbChannels == 2) {
br.skip(3);
} else {
br.skip(5);
}
nbGranules = 2;
for (int ch = 0; ch < s.nbChannels; ch++) {
ctx.granules[ch][0].scfsi = 0; // all scale factors are transmitted
ctx.granules[ch][1].scfsi = br.read(4);
}
}
for (int gr = 0; gr < nbGranules; gr++) {
for (int ch = 0; ch < s.nbChannels; ch++) {
Granule g = ctx.granules[ch][gr];
g.part23Length = br.read(12);
g.bigValues = br.read(9);
if (g.bigValues > 288) {
log.error(String.format("bigValues too big %d", g.bigValues));
return MP3_ERROR;
}
g.globalGain = br.read(8);
// if MS stereo only is selected, we precompute the
// 1/sqrt(2) renormalization factor
if ((s.modeExt & (MODE_EXT_MS_STEREO | MODE_EXT_I_STEREO)) == MODE_EXT_MS_STEREO) {
g.globalGain -= 2;
}
if (s.lsf != 0) {
g.scalefacCompress = br.read(9);
} else {
g.scalefacCompress = br.read(4);
}
boolean blocksplitFlag = br.readBool();
if (blocksplitFlag) {
g.blockType = br.read(2);
if (g.blockType == 0) {
log.error(String.format("invalid block type"));
return MP3_ERROR;
}
g.switchPoint = br.read1();
for (int i = 0; i < 2; i++) {
g.tableSelect[i] = br.read(5);
}
for (int i = 0; i < 3; i++) {
g.subblockGain[i] = br.read(3);
}
initShortRegion(g);
} else {
g.blockType = 0;
g.switchPoint = 0;
for (int i = 0; i < 3; i++) {
g.tableSelect[i] = br.read(5);
}
// compute Huffman coded region sizes
int regionAddress1 = br.read(4);
int regionAddress2 = br.read(3);
initLongRegion(g, regionAddress1, regionAddress2);
}
regionOffset2size(g);
computeBandIndexes(g);
g.preflag = 0;
if (s.lsf == 0) {
g.preflag = br.read1();
}
g.scalefacScale = br.read1();
g.count1tableSelect = br.read1();
}
}
if (ctx.aduMode == 0) {
int currentPosition = br.getBytesRead();
int copyLength = ctx.header.frameSize - (currentPosition - frameStart);
int bitsToSkip = bb.getBitsWritten() - bb.getBitsRead() - (mainDataBegin << 3);
for (int i = 0; i < copyLength; i++) {
bb.writeByte(br.readByte());
}
bb.skip(bitsToSkip);
}
for (int gr = 0; gr < nbGranules; gr++) {
for (int ch = 0; ch < s.nbChannels; ch++) {
Granule g = ctx.granules[ch][gr];
g.granuleStartPosition = bb.getBitsRead();
if (s.lsf == 0) {
// MPEG1 scale factors
int slen1 = slen_table[0][g.scalefacCompress];
int slen2 = slen_table[1][g.scalefacCompress];
if (g.blockType == 2) {
int n = g.switchPoint != 0 ? 17 : 18;
int j = 0;
if (slen1 != 0) {
for (int i = 0; i < n; i++) {
g.scaleFactors[j++] = bb.read(slen1);
}
} else {
for (int i = 0; i < n; i++) {
g.scaleFactors[j++] = 0;
}
}
if (slen2 != 0) {
for (int i = 0; i < 18; i++) {
g.scaleFactors[j++] = bb.read(slen2);
}
for (int i = 0; i < 3; i++) {
g.scaleFactors[j++] = 0;
}
} else {
for (int i = 0; i < 21; i++) {
g.scaleFactors[j++] = 0;
}
}
} else {
int sc[] = ctx.granules[ch][0].scaleFactors;
int j = 0;
for (int k = 0; k < 4; k++) {
int n = (k == 0 ? 6 : 5);
if ((g.scfsi & (0x8 >> k)) == 0) {
int slen = (k < 2 ? slen1 : slen2);
if (slen != 0) {
for (int i = 0; i < n; i++) {
g.scaleFactors[j++] = bb.read(slen);
}
} else {
for (int i = 0; i < n; i++) {
g.scaleFactors[j++] = 0;
}
}
} else {
// simple copy from last granule
for (int i = 0; i < n; i++) {
g.scaleFactors[j] = sc[j];
j++;
}
}
}
g.scaleFactors[j++] = 0;
}
} else {
int tindex;
int tindex2;
int[] slen = new int[4];
// LSF scale factors
if (g.blockType == 2) {
tindex = g.switchPoint != 0 ? 2 : 1;
} else {
tindex = 0;
}
int sf = g.scalefacCompress;
if ((s.modeExt & MODE_EXT_I_STEREO) != 0 && ch == 1) {
// intensity stereo case
sf >>= 1;
if (sf < 180) {
lsfSfExpand(slen, sf, 6, 6, 0);
tindex2 = 3;
} else if (sf < 244) {
lsfSfExpand(slen, sf - 180, 4, 4, 0);
tindex2 = 4;
} else {
lsfSfExpand(slen, sf - 244, 3, 0, 0);
tindex2 = 5;
}
} else {
// normal case
if (sf < 400) {
lsfSfExpand(slen, sf, 5, 4, 4);
tindex2 = 0;
} else if (sf < 500) {
lsfSfExpand(slen, sf - 400, 5, 4, 0);
tindex2 = 1;
} else {
lsfSfExpand(slen, sf - 500, 3, 0, 0);
tindex2 = 2;
g.preflag = 1;
}
}
int j = 0;
for (int k = 0; k < 4; k++) {
int n = lsf_nsf_table[tindex2][tindex][k];
int sl = slen[k];
if (sl != 0) {
for (int i = 0; i < n; i++) {
g.scaleFactors[j++] = bb.read(sl);
}
} else {
for (int i = 0; i < n; i++) {
g.scaleFactors[j++] = 0;
}
}
}
for (; j < 40; j++) {
g.scaleFactors[j] = 0;
}
}
exponentsFromScaleFactors(g, exponents);
// read Huffman coded residue
huffmanDecode(g, exponents);
}
if (s.mode == MP3_JSTEREO) {
computeStereo(ctx.granules[0][gr], ctx.granules[1][gr]);
}
for (int ch = 0; ch < s.nbChannels; ch++) {
Granule g = ctx.granules[ch][gr];
reorderBlock(g);
computeAntialias(g);
computeImdct(g, ctx.sbSamples[ch], 18 * gr * SBLIMIT, ctx.mdctBuf[ch]);
}
}
return nbGranules * 18;
}